Titanium-made plate-type heat exchanger and production method therefor

ABSTRACT

The present invention provides a titanium-made plate-type heat exchanger comprising first-fluid flow paths and second-fluid flow paths arranged alternately, which is formed by joining titanium-made constituting members, wherein: a titanium-zirconium based brazing solder containing 20 to 40 wt. % of titanium and 20 to 40 wt. % of zirconium, which melts under 880° C., is coated over positions to be connected of the constituting members, and brazing solder coated constituting members are heated under 880° C. in an vacuum and/or inert gas atmosphere. The present invention also provides a production method of the heat exchanger, which can prevent titanium-made constituting members of the heat exchanger from being deteriorated due to over-heating.

FIELD OF THE INVENTION

The present invention relates to a production method of a titanium-madeplate-type heat exchanger.

RELATED ART

A conventional titanium-made plate-type heat exchanger is disclosed inJapanese laid open patent No.2002-35929. In the heat exchanger by thisinvention, herringbone patterned titanium plates are layered such thatherringbone patterns of the neighboring plates are arranged in oppositedirections each other, and first-fluid flow paths and second-fluid flowpaths formed by gaps between the two neighboring plates are alternatelyarranged so that heat is exchanged between the two fluids.

The above-mentioned heat exchanger is produced according to thefollowing steps: positions to be connected on respective herringboneplates are coated with or filled by a brazing solder; the coated orfilled plates are placed in a vacuum heating furnace and the plates aredegassed as reducing the pressure of the furnace and gradually raisingthe temperature of the furnace; and after a required reduced pressure isattained, coated or filled positions are brazed by heating the platesover 850° C.

However, the conventional titanium-made plate-type heat exchanger hasthe following problems.

(1) Since herringbone patterns are formed by concave strips with achevroned cross section, two neighboring plates are contacted on concaveedge points of respective concave strips crossing each other.Consequently, connected positions by the brazing solder show a point topoint connection pattern so that a connected strength between theneighboring plates is low. As a result, a pressure-resistant performanceof the flow paths of the heat exchanger is not so good.

(2) Since a heat transfer area of fluid flow paths formed by the twoherringbone plates corresponds to surface areas of the herringboneplates, a heat transfer area per unit volume of the heat exchanger isnot so large. Consequently, a heat radiating performance of the flowpaths is not so good.

(3) When the plates are brazed at a temperature more than thetransformation temperature (882° C.) of α-titanium, the herringboneplates are deteriorated, which means a durability of the heat exchangeris deteriorated.

And in producing the conventional titanium-made plate-type heatexchanger, since the herringbone plates are brazed over 850° C., theyare deteriorated. Because when the brazing solder is heated over 850°C., sometimes the titanium-made plates are heated over thetransformation temperature (882° C.) of α-titanium so that these platesare deteriorated.

The present invention is carried out in order to solve the problemsmentioned above, and provides:

-   -   (1) A production method of a titanium-made plate-type heat        exchanger having fluid flow paths with a pressure resistant        performance, an excellent heat radiating performance and an        excellent durability;    -   (2) A method to produce a titanium-made plate-type heat        exchanger capable of preventing titanium members constituting        the fluid flow path from deteriorating due to over-heating.

DISCLOSURE OF THE INVENTION

A titanium-made plate-type heat exchanger provided by the presentinvention in which flow paths of a first fluid and a second fluid arealternately arranged such that heat can be exchanged between the twofluids and respective flow paths are formed by connecting titaniumplates; the heat exchanger comprises a flat container having an inlet ofone of the fluids formed on one end and an outlet of the fluid formed onthe other end; an offset-type titanium plate fin connected to thetitanium plates on its both sides and accommodated in the flat containerbetween the inlet and the outlet, wherein: the titanium plate fin andthe titanium plates are connected by a Ti—Zr type brazing solder, whichmelts under 880° C., containing 20 to 40 wt. % of titanium and 20 to 40wt. % of zirconium.

And a production method of a titanium-made plate-type heat exchangerprovided by the present invention in which flow paths of a first fluidand flow paths of a second fluid alternately arranged such that heat canbe exchanged between the two fluids, wherein the production method forforming the flow paths by connecting a titanium-made flat containerhaving an inlet of one of the fluids formed on one end and an outlet ofthe fluid formed on the other end to an offset-type titanium plate finaccommodated in the flat container and connected to the inner side ofthe container via top ends of concave strips of the titanium plate finso as to form a plane to plane connection, comprises steps of: coating abrazing paste over positions to be connected of said constitutingmembers by using a paste supply machine, wherein the brazing paste isprepared by atomizing an alloy comprising a Ti—Zr type brazing solder,which melts under 880° C., containing 20 to 40 wt. % of titanium and 20to 40 wt. % of zirconium so as to obtain a powdered alloy, which ismixed with a neutral binder so that the brazing paste is prepared; andheating said brazing solder coated constituting members under 880° C. inan vacuum and/or inert gas atmosphere (hereinafter referred as“production method of heat exchanger”).

In the heat exchanger by the present invention, since top ends ofparallel concave strips constituting a pattern of the titanium plate finconstitute a plane which contacts the titanium plate in a plane to planerelation, the titanium plate fin and the titanium are connected by thebrazing solder in the form of the plane to plane connection.Consequently, a connected area between the titanium plate and thetitanium plate fin is enlarged so that a connected strength is raised.

In the titanium plate fin, the concave strips constituting the patternof the titanium plate fin show an offset arrangement. Namely, both wallsof the concave strip T having a trapezoidal cross section are bentinside with a predetermined pitch. Consequently, a surface area of thetitanium plate fin is enlarged so that a heat transfer area of the heatexchanger per unit area is raised.

Further, since a connection between the titanium plates and a connectionbetween the titanium plate and the titanium plate fin are attained byusing the brazing solder which melts under 880° C., namely under thetransformation temperature (882° C.) of α-titanium, the above-mentionedtitanium plates to be connected are not heated over 880° C. As a result,both titanium plates are not deteriorated due to over-heating.

And in the production method of the heat exchanger by the presentinvention, since the connection between the titanium plates and theconnection between the titanium plate and the titanium plate fin areattained by using the brazing solder which melts under 880° C., theabove-mentioned titanium plates to be connected are not heated at thetransformation temperature of α-titanium, when brazed. As a result, theproduction method by the present invention can prevent both titaniumplates from being deteriorated due to over-heating.

Particularly, the production method by the present invention employs thepaste-type brazing solder, since alloys used for the brazing solder bythe present invention have high hardness and very low malleability, theycan not be obtained in the form of a plate or a bar. Therefore thealloys are atomized in Ar gas atmosphere to obtain powdered alloys,which are mixed with the neutral binder to obtain the paste, which issupplied as the brazing solder to portions to be connected by utilizingthe paste supply machine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically illustrating an arrangementof the titanium-made plate-type heat exchanger obtained by a preferredproduction method by the present invention.

FIG. 2 is an exploded perspective view of the titanium-made plate-typeheat exchanger shown in FIG. 1.

FIG. 3 is a perspective view of the titanium-made plate-type heatexchanger in FIG. 2 viewed from the opposite direction.

FIG. 4A is a plan view of first unit plate and FIG. 4B is a plan view ofthe second unit plate in FIG. 3.

FIG. 5 is a perspective view illustrating main portions of titaniumplate fins in FIG. 4.

BEST PREFERRED EMBODIMENTS BY THE PRESENT INVENTION

Hereinafter the embodiment by the present invention is explained asreferring to drawings FIG. 1 is a view schematically illustrating thearrangement of the titanium-made plate-type heat exchangers (hereinafterreferred as “heat exchanger”) obtained by the production method of thepreferred embodiment.

As shown in FIG. 1, flow paths B, D and F for a first fluid X and flowpaths A, C, E and G for a second fluid Y are alternately arranged sothat heat is exchanged between the two fluids X and Y.

The first fluid X flows into the flow paths B, D and F from respectiveinlets 1 and flows out from respective outlets 2. The second fluid Yflows into the flow paths A, C, E and G from respective inlets 3 andflows out from respective outlets 4.

A reference numeral “5” is passages for the fluid X arranged in the flowpaths A, C and E and communicated with the inlets 1. A reference numeral“6” is passages for the fluid X arranged in the flow paths A, C and Eand communicated with outlets 2.

A reference numeral “7” is passages for the fluid Y arranged in the flowpaths B, D and F and communicated with the inlets 3. A reference numeral“8” is passages for the fluid Y arranged in the flow paths B, D and F.Reference numerals “9” and “10” are shut-off paths arranged in the flowpath G.

FIGS. 2 and 3 are exploded views of the above-mentioned heat exchanger.

As shown in FIGS. 2 and 3, the heat exchanger is constituted in thefollowing manner. First unit plates (hereinafter referred as “firstunit”) U₁ and second unit plates (hereinafter referred as “second unit”)U₂ are alternately layered and connected each other. Bosses 11, 12, 13and 14 are attached to the front end second unit U₂ and a cover plate Pis attached to the back end second unit U₂.

As shown in FIGS. 4A and 4B, the first and second units U₁ and U₂ arerespectively constituted by titanium plates 15 having upright peripheralwalls 15 a around, titanium guide plates 16, 16 arranged at bothlongitudinal ends of the titanium plates and two titanium plate fins 17arranged between the titanium guide plates 16, 16.

Two holes 18 are arranged at each end of the titanium plate 15 so thatfour holes 18 are symmetrically arranged on both ends of the titaniumplate.

walls 15 a of the respective titanium plates. The titanium plate fin 17is connected with the titanium plate 15 via top end of the concave stripT. The both sides of the titanium guide plate 16 are connected to thetitanium plates 15. The above-mentioned respective connected portionsare connected in the form of plane to plane connection.

The holes 18 of the titanium plate 15 and the holes 19 of the titaniumguide plate 16, which form passages (the passages 5 to 8 in FIG. 1) forthe fluids, are connected via peripheral portions of the respectiveholes.

The heat exchanger by the embodiment is produced in the followingmanner.

-   -   (1) A brazing solder is coated on the portions to be connected        of the first units U₁, second units U₂, the cover plate P and        the bosses 11 to 14, and then coated members with the brazing        solder are assembled so that a heat exchanger assembly is        prepared.

For example, one of the brazing solders shown in TAB.1, which melt under880° C., is used as a brazing solder.

Both brazing solders contain mainly titanium and zirconium. In otherwords, Ti—Zr alloys are employed as the brazing solders. TAB.1 indicatesthat a brazing solder containing no Ni metal such as No.1 product can beused as a brazing solder and rather small amount of Cu metal is requiredas a constituent of the brazing solders. TABLE 1 Product Composition(wt. %) Melting # Ti Zr Cu Ni Point (° C.) No.1 37.5 37.5 25 0 820-840No.2 37.5 37.5 15 10 810-830

Since the products in TAB.1 have high hardness and very lowmalleability, they can not be obtained in the form of a plate or a bar.Consequently, in order to employ the products as a brazing solder, theyare atomized in argon gas atmosphere to obtain powdered products, whichare mixed with a neutral binder to obtain a paste, which is supplied asthe brazing solder to portions to be connected by utilizing a pastesupply machine.

Then the prepared heat exchanger assembly is placed in a vacuum heatingfurnace and heated gradually after the pressure in the furnace is

1. A production method of a titanium-made plate-type heat exchangercomprising flow paths of a first fluid and flow paths of a second fluidalternately arranged such that heat can be exchanged between the twofluids, said production method for forming said flow paths by connectinga titanium-made flat container having an inlet of one of the fluidsformed on one end and an outlet of the fluid formed on the other end toan offset-type titanium plate fin accommodated in said flat containerand connected to the inner side of said container via top ends ofconcave strips of said titanium plate fin so as to form a plane to planeconnection, comprising steps of: coating a brazing paste over positionsto be connected of said constituting members by using a paste supplymachine, wherein said brazing paste is prepared by atomizing an alloycomprising a Ti—Zr type brazing solder, which melts under 880° C.,containing 20 to 40 wt. % of titanium and 20 to 40 wt. % of zirconium soas to obtain a powdered alloy, which is mixed with a neutral binder sothat said paste is prepared; and heating said brazing solder coatedconstituting members under 880° C. in an vacuum and/or inert gasatmosphere.
 2. (canceled)